[Rhino-X-Java - hiddenField] Accessing Java members from Rhino JS Engine

[Rhino-X-Java - hiddenField]

[Rhino-X-Java - hiddenField]
Accessing Java members from Rhino JS Engine

_init.sh

#!/bin/sh
URL=https://gist.github.com/Oifan/22df3556ea46a41f771987b93942ca34/raw/43a252ce8bce19991d59636dc562ea3f2c6e770f
mkdir lib
mkdir src
wget "$URL/hidden.sh"
wget -O src/mk.sh "$URL/src%2523mk.sh"
wget -O src/HiddenField.java "$URL/src%2523HiddenField.java"
wget -O src/hiddenField.js "$URL/src%2523hiddenField.js"
chmod 755 hidden.sh src/mk.sh
echo '[i] Download COMPLETE :-)'
echo ' * To COMPILE this example        --> Run src/mk.sh'
echo ' * To RUN this (after COMPILE)    --> Run hidden.sh'

hidden.sh

#!/bin/sh
RHINO_VER=1.7.10
#RHINO_VER=1.7.9

[ -f "lib/rhino-$RHINO_VER.jar" ] || wget -Plib "http://central.maven.org/maven2/org/mozilla/rhino/$RHINO_VER/rhino-$RHINO_VER.jar"

CPSEP=':'
[ -z "${WINDIR}" ] || CPSEP=';'
JAVACP=lib/hidden.jar${CPSEP}lib/rhino-$RHINO_VER.jar
java -cp "$JAVACP" org.mozilla.javascript.tools.shell.Main -f src/hiddenField.js

src#HiddenField.java

public class HiddenField {

	public int hidden = 10;

	public boolean hidden() {
		return true;
	}

}

src#hiddenField.js

'use strict';
importClass( java.lang.Class );
importClass( org.mozilla.javascript.Context );
importClass( org.mozilla.javascript.Scriptable );
importClass( Packages.HiddenField );


function getFieldFrom (obj, fldName) {
	var field = obj.getClass().getField( fldName );
	return field.get( obj );
}

function invokeDeclaredMethod (obj, clazz, methName, methParamTypes, methParams, force) {
	var method = clazz.getDeclaredMethod( methName, methParamTypes );
	if ( force )
		method.setAccessible( true );
	var result = method.invoke( obj, methParams );
	if ( force )
		method.setAccessible( false );
	return result;
}

function showInfo (member) {
	print( 'typeof\t= ' + typeof member );
	if (typeof member == 'function') {
		print( '------ toSource() ------' );
		print( member.toSource() );
	} else {
		print( 'value\t= ' + member + '\n' );
	}
}

//---------------------------[ MAIN PROGRAM ]---------------------------

print( '[ ' + Context.currentContext.implementationVersion + ' ]\n' );

var hidnFldObj = new Packages.HiddenField();

print( '#######[ PROBLEM DESCRIPTION ]#######\n' );

print( 'Having an instance of class HiddenField (see src/HiddenField.java),');
print( 'we want to access its member -- public int hidden.');
print( 'In Java this could be done with: "new HiddenField().hidden".\n');

print( '########[ EXPECTED BEHAVIOR ]########\n' );

print( "****[ APPROACH 0: using Java reflection ]****" );
var hidnFldMembr0 = getFieldFrom( hidnFldObj, 'hidden' );
showInfo( hidnFldMembr0 );
					// typeof	= object
					// value	= 10

print( '########[  ACTUAL BEHAVIOR  ]########\n' );

print( "****[ APPROACH 1: new Packages.HiddenField().hidden ]****" );
var hidnFldMembr1 = hidnFldObj.hidden;
showInfo( hidnFldMembr1 );
					// typeof = function
					// ------ toSource() ------
					// function hidden() {/*
					// boolean hidden()
					// */}

print( "****[ APPROACH 2: new Packages.HiddenField()['hidden'] ]****" );
var hidnFldMembr2 = hidnFldObj['hidden'];
showInfo( hidnFldMembr2 );
					// *** SAME AS 'APPROACH 1' ***

print( "****[ APPROACH 3: using Rhino's JavaMembers.lookupClass and JavaMembers.get ]****" );

var javaMembersClz = Class.forName( 'org.mozilla.javascript.JavaMembers' );
var javaMembers = invokeDeclaredMethod(
	null, javaMembersClz, 'lookupClass',
	[ Scriptable, Class, Class, java.lang.Boolean.TYPE ],
	[ this, HiddenField, HiddenField, false ],
	true );
var hidnFldMembr3 = invokeDeclaredMethod(
	javaMembers, javaMembersClz, 'get',
	[ Scriptable, java.lang.String, java.lang.Object, java.lang.Boolean.TYPE ],
	[ this, 'hidden', hidnFldObj, false ],
	true );
showInfo( hidnFldMembr3 );
					// *** SAME AS 'APPROACH 1' ***

// TODO see also	https://stackoverflow.com/questions/10483422/intercept-field-access-of-java-objects-in-rhino

src#mk.sh

#!/bin/sh
javac HiddenField.java
jar cvf ../lib/hidden.jar *.class *.java
[ -d classes ] || mkdir classes
mv *.class classes/

To download & run this example, do following:

1. download & run _init.sh --> this will download all other files from this gist
2. follow instructions at the end of _init.sh --> to compile and run this example

To summarize it in 3 lines:
wget https://gist.github.com/Oifan/22df3556ea46a41f771987b93942ca34/raw/8717635de51412f15139c0dfbdb8b61cb2cbe9dd/_init.sh && . _init.sh
cd src && ./mk.sh
cd .. && ./hidden.sh